Structure and Kinematics of CO (J=2-1) Emission in the Central Region of NGC 4258

Abstract

We present 12CO (J=2-1) observations towards the central region of the Seyfert 2 galaxy NGC 4258 with the Submillimeter Array (SMA). Our interferometric maps show two arm-like elongated components along the major axis of the galaxy, with no strong nuclear concentration. The CO (2-1) morphology and kinematics are similar to previous CO (1-0) results. The velocity field of the components agrees with the general galactic rotation, except for the east elongated component, which shows a significant velocity gradient along the east-west direction. In order to account for the velocity field, we propose the kinematical model where the warped rotating disk is also expanding. The line ratio of CO(2-1)/CO(1-0) reveals that the eastern component with the anomalous velocity gradient appears to be warmer and denser. This is consistent with the gas in this component being closer to the center, being heated by the central activities, and possibly interacted by expanding motions from the nuclear region.

accepted for publication in ApJ, 21 pages, 8 figures

References in corpus (6)

• The Submillimeter Array
• The BIMA Survey of Nearby Galaxies (BIMA SONG). II. The CO Data
• The Geometry of and Mass Accretion Rate through the Maser Accretion Disk in NGC 4258
• SMA CO(J=3-2) interferometric observations of the central region of M51
• The Virgo High-Resolution CO Survey. II. Rotation Curves and Dynamical Mass Distributions
• X-ray Luminosity and Absorption Column Fluctuations in the H2O Maser Galaxy NGC 4258 from Weeks to Years

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• The radio luminosity, black hole mass and Eddington ratio for quasars from the Sloan Digital Sky Survey
• Millimeter line observations toward four local galaxies
• Blasts and shocks in the disc of NGC 4258